An investigation of the use of rectangular insecticide-treated nets for malaria control in Chipinge District, Zimbabwe: a descriptive study

In 2007, Zimbabwe government distributed rectangular insecticide treated nets in Chipinge District, covering 100% of population at risk. However, malaria morbidity continued increasing from 492/1000 (49.2%) in 2007 to 667/1000 (66.7%) in 2008. A study was conducted in Chipinge District in May 2009 to investigate the use of rectangular insecticide treated nets and factors affecting their use in malaria prevention. A descriptive cross-sectional study was conducted. Quantitative and qualitative methods were triangulated to assess utilisation of rectangular insecticide treated nets. Five interviewers administered 380 questionnaires to senior matriarchs selected from five wards, with 19,667 sampling frame (19,667/380 = 52). Five focus group discussions were conducted. Quantitative data were analysed using Statistical Package for the Social Sciences, while qualitative data were summarised into thematic areas. Approximately, 95% of respondents knew that malaria was caused by mosquito bites. Perception of nets as malaria preventative measure was high (88%). Utilization of rectangular insecticide treated nets was low (33%) with 81% of those not using them expressed difficulty procedures of mounting them and unavailability of related accessories as main reasons. People preferred conical insecticide treated nets (84%) compared to rectangular insecticide treated nets (15%). Although the Chipinge people accepted insecticide treated nets for malaria prevention, procedure of mounting rectangular insecticide treated nets and accessing related accessories prevented consistent use.In order for insecticide treated net project to have impact on malaria prevention, priority should be given to conical shape or rectangular shape with adequate accessories like wire nails and strings or twine

Bionomics of malaria vectors in Mutare and Mutasa districts of Manicaland province, Zimbabwe

Bionomics of malaria vectors including species composition, resting and biting behaviour and insecticide resistance are important for insecticide-based malaria control and interventions. The lack of data on malaria vector species composition and relative abundance, resting and biting behaviour, as well as insecticide resistance, make the development of target control measures problematic in Mutare and Mutasa Districts. It is imperative to elucidate, characterize, and identify all members of the An. funestus group and the An. gambiae complex to determine their resting and biting behaviour, host-seeking activities, disease relationships, and resistance to insecticides. A longitudinal study was carried out to investigate the bionomics of malaria vector mosquitoes in Mutare and Mutasa Districts. Anopheline larval and adult sampling was conducted from May 2013 to December 2014 using scooping, pyrethrum spray catch, prokopac aspirator, exit window trap, pit shelter, and Centers for Disease Control (CDC) light trap methods. Indoor and outdoor resting mosquitoes were collected in randomly selected houses and pit shelters, respectively. Mosquitoes sampled by light traps were divided into two cohorts. In one cohort, traps were left overnight and mosquitoes collected the following morning, while in the other set, mosquitoes were collected hourly throughout the night. Mosquito samples for insecticide resistance testing were divided into two subsamples. One subsample was used immediately for WHO susceptibility assays and the other batch was allowed to oviposit in the insectary at the National Institute of Health Research, and females from the F1 progeny were used in further susceptibility assays. Mosquitoes were identified using morphological keys and polymerase chain reaction (PCR) techniques. The PCR-based assays showed the presence of four sibling species: Anopheles funestus sensu stricto (90.8%, 267/294) and An. leesoni (5.1%, 15/294) of the An. funestus group and An. arabiensis (41.9%, 13/31) and An. quadriannulatus (48.4%, 15/31) of the An. gambiae complex. Of the two malaria vectors, An. funestus sensu stricto was more abundant (95.4%, 267/280) than An. arabiensis (4.6%, 13/280). Endophilic collections of the An. funestus group and the An. gambiae complex were five times greater than exophilic catches. Nearly 90% endophilic An. funestus populations were collected on sprayable surfaces and the remainder was caught on unsprayable surfaces. Of the sprayable surfaces catches, 56% were collected on the roofs; with 44% on the walls. Of the gravid An. funestus caught, nearly two-thirds (218/330) were collected exiting recently pyrethroid-treated structures, with a 24-hour mortality of less than 10%. The CDC light trap catches were more abundant indoors (68%) than outdoors (32%). Anopheles funestus showed variable indoor and outdoor flight activity rhythms, with two peaks during the night; between 22:00-23:00 hours and 02:00-04:00 hours. Human blood index was 64.3%, with Plasmodium falciparum infection rate of 1.8%. Wild caught females showed resistance to lambda-cyhalothrin (3.3% mortality), deltamethrin (12.9% mortality), etofenprox (9.2% mortality), and bendiocarb (11.7% mortality).F1 An. funestus females showed resistance to deltamethrin (14.5% mortality), lambda-cyhalothrin (6.9 % mortality), etofenprox (8.3% mortality), and bendiocarb (16.8% mortality), but were susceptible to DDT and pirimiphos-methyl (100% mortality). Intensity resistance assay to bendiocarb had 100% mortality, while deltamethrin, lambda-cyhalothrin, and etofenprox had increased knockdown times with mortalities ranging between 66.7 and 92.7% after 24-hour exposures. The present work revealed important information on the behaviour of malaria vector mosquitoes in Mutare and Mutasa Districts, which if not addressed might threaten gains made in malaria control in the study area. It is imperative to change house-spraying insecticide from pyrethroids to organophosphates or DDT (organochlorine), develop an insecticide resistance management plan, provide extension lances to the house-spraying programme, complement mosquito nets with the use of mosquito repellents and long clothes, and establish a monitoring programme to determine the occurrence and distribution of An. funestus populations in Manicaland Province

Nationwide assessment of insecticide susceptibility in Anopheles gambiae populations from Zimbabwe.

BACKGROUND: The scale-up of malaria interventions in sub-Saharan Africa has been accompanied by a dramatic increase in insecticide resistance in Anopheles spp. In Zimbabwe resistance to pyrethroid insecticides was reported in Gokwe District in 2008. This study reports results of the first nation-wide assessment of insecticide susceptibility in wild populations of Anopheles gambiae sensu lato (s.l.) in Zimbabwe, and provides a comprehensive review of the insecticide resistance status of An. gambiae s.l. in southern African countries. METHODS: World Health Organization (WHO) insecticide susceptibility tests were performed on 2,568 field collected mosquitoes originating from 13 sentinel sites covering all endemic regions in Zimbabwe in 2011-2012. At each site, 24-hour mortality and knock-down values for 50% and 90% of exposed mosquitoes (KD50 and KD90, respectively) were calculated for pools of 20-84 (mean, 54) mosquitoes exposed to 4% DDT, 0.1% bendiocarb, 0.05% λ-cyhalothrin or 5% malathion. Susceptibility results from Zimbabwe were compiled with results published during 2002-2012 for all southern African countries to investigate the resistance status of An. gambiae s.l. in the region. RESULTS: Using WHO criteria, insecticide resistance was not detected at any site sampled and for any of the insecticide formulations tested during the malaria transmission season in 2012. Knock-down within 1 hr post-insecticide exposure ranged from 95% to 100%; mortality 24 hours post-insecticide exposure ranged from 98% to 100%. Despite the lack of insecticide resistance, high variability was found across sites in KD50 and KD90 values. A total of 24 out of 64 (37.5%) sites in southern Africa with reported data had evidence of phenotypic insecticide resistance in An. gambiae s.l. to at least one insecticide. CONCLUSION: Despite a long history of indoor residual spraying of households with insecticide, up to 2012 there was no evidence of phenotypic resistance to any of the four insecticide classes in An. gambiae s.l. collected across different eco-epidemiological areas in Zimbabwe. Results reinforce the need for careful monitoring over time in sentinel sites in order to detect the potential emergence and propagation of insecticide resistance as insecticidal vector control interventions in Zimbabwe continue to be implemented

Progress towards malaria elimination in Zimbabwe with special reference to the period 2003–2015

Abstract Background An intensive effort to control malaria in Zimbabwe has produced dramatic reductions in the burden of the disease over the past 13 years. The successes have prompted the Zimbabwe’s National Malaria Control Programme to commit to elimination of malaria. It is critical to analyse the changes in the morbidity trends based on surveillance data, and scrutinize reorientation to strategies for elimination. Methods This is a retrospective study of available Ministry of Health surveillance data and programme reports, mostly from 2003 to 2015. Malaria epidemiological data were drawn from the National Health Information System database. Data on available resources, malaria control strategies, morbidity and mortality trends were analysed, and opportunities for Zimbabwe malaria elimination agenda was perused. Results With strong government commitment and partner support, the financial gap for malaria programming shrank by 91.4% from about US$13 million in 2012 to US$1 million in 2015. Vector control comprises indoor residual house spraying (IRS) and long-lasting insecticidal nets, and spray coverage increased from 28% in 2003 to 95% in 2015. Population protected by IRS increased also from 20 to 96% for the same period. In 2009, diagnostics improved from clinical to parasitological confirmation either by rapid diagnostic tests or microscopy. Artemisinin-based combination therapy was used to treat malaria following chloroquine resistance in 2000, and sulfadoxine–pyrimethamine in 2004. In 2003, there were 155 malaria cases per 1000 populations reported from all health facilities throughout the country. The following decade witnessed a substantial decline in cases to only 22 per 1000 populations in 2012. A resurgence was reported in 2013 (29/1000) and 2014 (39/1000), thereafter morbidity declined to 29 cases per 1000 populations, only to the same level as in 2013. Overall, morbidity declined by 81% from 2003 to 2015. Inpatient malaria deaths per 100,000 populations doubled in 4 years, from 2/100,000 to 4/100,000 populations in 2012–2015 respectively. Twenty of the 47 moderate to high burdened districts were upgraded from control to malaria pre-elimination between 2012 and 2015. Conclusions A significant progress to reduce malaria transmission in Zimbabwe has been made. While a great potential and opportunities to eliminate malaria in the country exist, elimination is not a business as usual approach. Instead, it needs an improved, systematic and new programmatic strategy supported strongly by political will, sustained funding, good leadership, community engagement, and a strong monitoring and evaluation system all year round until the cessation of local transmission

Biting behaviour of Anopheles funestus populations in Mutare and Mutasa districts, Manicaland province, Zimbabwe: Implications for the malaria control programme

Background & objectives: Biting behaviour of Anopheles funestus in Mutare and Mutasa districts, Zimbabwe, is little understood. An investigation was conducted to primarily compare indoor and outdoor biting behaviour of the mosquito, as well as blood meal sources and sporozoite rates. Methods: Monthly adult anopheline sampling was conducted from October 2013 to September 2014 using Centers for Disease Control light-traps, pyrethrum spray catch and artificial pit shelter methods. Mosquitoes sampled by light-traps were divided into two cohorts. In one cohort, traps were left overnight and mosquitoes were collected the following morning, while in the other set, mosquitoes were collected hourly from 1800-0600 hrs . Collected females were identified using morphological characters and categorised according to their abdominal status. Polymerase chain reaction was used to identify An. funestus sibling species and blood meal sources. Infection rate was tested by enzyme-linked immunosorbent assay. Results: Morphological identification showed that indoor and outdoor catches comprised Anopheles funestus (98.3%) and Anopheles gambiae s.l. (1.7%). Of the 2268 mosquitoes collected, 66.2% were caught by light-traps, and 33.8% were caught resting indoors and outdoors. Anopheles funestus and An. gambiae s.l. were trapped more abundantly indoors (68%) than outdoors (32%). Both indoor and outdoor An. funestus densities were higher in wet (4.3) than dry season (1.8). In Burma Valley and Zindi areas, An. funestus demonstrated variable nocturnal indoor and outdoor flight activity rhythms, with two peaks during the night; between 2200-2300 hrs and 0200- 0400 hrs. Human blood index in An. funestus was 0.64, with Plasmodium falciparum infection rate of 1.8%. Interpretation & conclusion: The present work highlighted important information on the host-seeking behaviour, blood meal sources and infection rates in An. funestus. The information would be helpful in improving the vector control strategies